B Optimal Flexible Architecture

This appendix describes the Optimal Flexible Architecture standard. This standard is a set of configuration guidelines created to ensure well organized Oracle installations that are easier to maintain. It includes information about the following topics:

Oracle recommends that you use Optimal Flexible Architecture, specially if the database grows in size, or if you plan to have multiple databases.

B.1.1 Advantages of Multiple Oracle Homes and OFA

When you install Oracle database, you are installing one of the largest applications that your computer can support. Using multiple Oracle homes and Optimal Flexible Architecture provides many advantages when administering large databases. The following advantages are important:

Distribution of I/O across multiple disks prevents performance bottlenecks caused by multiple read or write commands issued simultaneously to a single drive.

Distribution of applications across multiple disks safeguards against database failures.

Login home directories are not at risk when database administrators add, move, or delete Oracle home directories.

Multiple databases, of different versions, owned by different users can coexist concurrently.

Software upgrades can be tested in an Oracle home in a separate directory from the Oracle home where your production database is located.

B.2 Changes to the Optimal Flexible Architecture for Oracle Database

For previous releases of Oracle Database, the Optimal Flexible Architecture recommended Oracle home path was similar to the following:

c:\oracle\ora92

Starting with Oracle Database 11g Release 1 (11.1), the Optimal Flexible Architecture recommended Oracle home path changed. The Optimal Flexible Architecture recommended Oracle home path is now similar to the following:

c:\app\username\product\11.2.0\dbhome_1

The ORACLE_BASE default does not contain version information but the default ORACLE_HOME does.

B.3.1 Top-Level Oracle Directory

When you install Oracle Database Optimal Flexible Architecture-compliant database, all subdirectories are under a top-level Oracle base directory, DRIVE_LETTER:\app\username, where DRIVE_LETTER is any hard drive.

B.3.2 Database File Names

Database files do not have the SID in the database file name. For example, the first control file is named control01.ctl. The SID in the file name is not necessary because all the database files for a particular database are placed in \oradata under a directory called DB_UNIQUE_NAME that is named for that database.

B.3.3 Database File Name Extensions

In an Optimal Flexible Architecture-compliant release, database file names have the following extensions:

.ctl for control files

.log for log files

.dbf for data files

B.4 Optimal Flexible Architecture Directory Naming Conventions

Optimal Flexible Architecture uses directory naming conventions that make it easy to identify the precise Oracle home and database name that is associated with a set of files. This section describes the naming conventions used for top-level directories of an Optimal Flexible Architecture-compliant database directory tree:

B.4.1 ORACLE_BASE Directory

ORACLE_BASE is the root of the Oracle directory tree. If you install an Optimal Flexible Architecture-compliant database using Oracle Universal Installer default settings, then ORACLE_BASE is DRIVE_LETTER:\app\username.

If you are installing Oracle Database for Microsoft Windows on a computer with no other Oracle software installed, then you can change the ORACLE_BASE directory before running Oracle Universal Installer. Most users do not need or want to do this.

Do not change the value of ORACLE_BASE after you run Oracle Universal Installer for the first time. If there is an existing ORACLE_BASE and you change it, then there is a conflict of Oracle base directories. If you create another ORACLE_BASE when the original ORACLE_BASE exists, then certain tools and the database are not able to find previously created files. They look for them in the new ORACLE_BASE instead of the original ORACLE_BASE.

See Also:

Your operating system documentation for instructions about editing environment variables

B.4.2 ORACLE_HOME Directory

The ORACLE_HOME directory is located under DRIVE_LETTER:\ORACLE_BASE, where DRIVE_LETTER:\is any hard drive, and contains subdirectories for Oracle software executables and network files.

If you install Oracle Database for Windows on a computer with no other Oracle software installed and you use default settings, then the first directory that you create is called \dbhome_1.

B.4.6 RECOVERY_AREA Directory

The recovery_area directory stores and manages files related to backup and recovery. It contains a subdirectory for each database on the system. A fast recovery area is an optional disk location that you can use to store recovery-related files such as control files and online redo log copies, archived logs, flashback logs, and Oracle Database Recovery Manager (RMAN) backups. Oracle and RMAN manage the files in the fast recovery area automatically.

This example shows how to create all Oracle homes within one Oracle base directory.

Install any Oracle Database that supports Optimal Flexible Architecture (Oracle Database Release 8.1.6 or later) on a computer with no other Oracle software installed and ensure that you accept the default settings for the Oracle home (for example, c:\app\username\product\11.2.0\dbhome_1).

Install any Oracle Database in a second Oracle home accepting the default settings.

In this example, you install each Oracle home into its own directory, but they all share the same Oracle base.

Install any Oracle Database that supports Optimal Flexible Architecture (Oracle Database 8.1.6 or later) on a computer with no other Oracle software installed and change the default Oracle Universal Installer settings for the first Oracle home (for example, from c:\oracle\ora81 to X:\xyz\oracle\abc).

Install any Oracle Database and change the default Oracle Universal Installer settings for the second Oracle home (for example, from c:\oracle\ora10 to X:\pqr).

B.6.1 Directory Naming

Top-level names of the Optimal Flexible Architecture directory tree differ between Windows and UNIX. However, main subdirectory names and file names are the same on both operating systems.

B.6.2 ORACLE_BASE Directory

On Windows, Oracle base is associated with an Oracle home directory. ORACLE_BASE is defined in the registry (for example, in HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\KEY_HOME_NAME).

On UNIX, ORACLE_BASE is associated with a UNIX user's environment.

B.6.3 Support for Symbolic Links on Windows

The goal of Optimal Flexible Architecture is to place all Oracle software under one ORACLE_BASE directory and to spread files across different physical drives as your databases increase in size.

On UNIX, although everything seems to be in one directory on the same hard drive, files can be on different hard drives if they are symbolically linked or have that directory as a mount point.

On Windows, you can use volume mount points to mount files on different hard drives to a single directory. You may have oradata directories on multiple drives, with data files in each one, on Windows version which does not support volume mount points.

Oracle recommends that you use one logical drive to store your database administration files and that you place other files, as needed, on other logical drives in an oradata\DB_UNIQUE_NAME directory.

In the following example, there are four logical drives for a database named prod:

c:\ contains an Oracle home and database administration files.

f:\ contains redo log files. The F:\ drive could also represent two physical drives that have been striped to increase performance.

g:\ contains one of the control files and all tablespace files. The G:\ drive could also use a RAID Level-5 configuration to increase reliability.